Publisher's Note: "Solution processed multilayer polymer light-emitting diodes based on different molecular weight host" (vol 109, 074516, 2011)

Solution processed multilayer polymer light-emitting diodes (PLEDs) based on different molecular weight host have been investigated. A PLED based on high molecular weight poly (vinyl carbazole) PVKH and low molecular weight poly (vinyl carbazole) PVKL, doped with iridium, tris(2-phenylpyidine) Ir(ppy)3 as a host-guest emitting layer (EML), shows a dramatic increase in device efficiency. When the PVKH was used as a hole transport electron blocking layer (HT-EBL), effective electron blocking was achieved, which leads to an increase exciton population in the phosphorescent zone. The use of low molecular weight PVKL as a host material in the top layer prevents barrier formation for hole transport from the poly(3,4-ethylenedioxy-thiophene) (PEDOT)–EBL to the EML. External quantum efficiency of 11%, current efficiencies of 38 cd/A, power efficiency of 13 lm/W and brightness of 7000 cd/m2, were obtained. The effect of the PVKH layer on the electrical and optical device characteristics was investigated. Simulation of the optical outcoupling using SETFOS 3.1 software is in agreed with the observed results and allowed us to predict the emissive dipole location and distribution in the EML layer. The effect of the PVKH on the exciton quenching by the electrodes was also investigated using time resolved fluorescence photon counting, which indicates weak exciton quenching by the PEDOT layer and the device enhancement predominantly achieved by exciton confinement in the emissive layer

The Role of Private School Principals in Total Quality Mangagement and its Relation with Educational Leadership Style

The study aimed to explore the roles of private school principals in total qualitymangagement and its relation with leadership style from the perspective of the teachers. A random sample of teachers (N=100) was selected from private schools in Muscat during the academic year 2015/2016. Two instruments were tailored to achieve the objective of the study. One, measured the role of principal in total quality management, and the other measured leadership style. The results revealed that principals of private schools use total quality management to a medium level and they follow the democratic style in their leadership. Also, there was a relationship between TQM and leadership style. The study offered few recommendations that may help implement TQM in private schools

Performance of High-volume Fly Ash Self-compacting Concrete Exposed to External Sulfate Attack

The high-volume fly ash concrete, HVFAC, could be defined as any concrete mix having fly ash content larger than 50 percent of the total cementitious materials content. Due to the availability of fly ash in large quantities globally with low cost, HVFAC could be considered as a solution for the environmental impact of Portland cements. In this study the durability of two high-volume fly ash self-compacting concrete, HVFASCC, mixes exposed to the effects of two sulfate aggressive solutions was investigated. The fly ash, class F, contents for these mixes were 50 and 60 percent by weight of Portland cement. The external sulfate attack was simulated by submerging the concrete specimens in 5 percent sodium and magnesium sulfate solutions separately for 240 days. Six mixes were produced for this purpose, they were: 2 reference mixes cured in water, 2 mixes submerged in Na2SO4 solution and 2 mixes submerged in MgSO4 solution. The testing program includes: slump flow, V-funnel, L-box, weight change, XRD and the strength tests: compressive, splitting and flexural strengths. The fly ash content has a positive effect on the rheology (workability) of all tested mixtures. In other words, increasing the cement replacement level from 50 to 60 percent has enhanced the filling ability, passing ability, and segregation resistance of the investigated SCC mixes. The test results show that the magnesium solution has the higher harmful effect on all mixes than the sodium solution. The replacements of Portland cement by the assigned percentages of fly ash have significantly increased the resistance of SCC to the external sulfate attack due to lime consuming reaction

A meta-analysis of meta-analyses of the effectiveness of FIFA injury prevention programmes in soccer

FIFA has a Medical and Research Centre (F-MARC) which has designed a comprehensive programme targeting muscle strength, kinaesthetic awareness, and neuromuscular control during static and dynamic movements to decrease injury risk for soccer players. A number of meta-analyses now exist on how effective FIFA's programmes to prevent and reduce injury actually are, with various degrees of injury reduction reported. This research aimed to carry out a systematic review and to meta analyse the existing meta-analyses so that a conclusion can be drawn on how effective the injury programmes are. Relevant studies were identified by searching five databases for the period January 1990 till 1 July 2018. Results of each meta-analysis were combined together using risk ratios (RR) in a summary meta-analysis. QUOROM checklist and AMSTAR 2 assessment were used to assess the quality of reporting and methodology in the meta-analyses. Four meta-analyses met the inclusion criteria covering fifteen primary studies. All four meta-analyses scored quite highly on QUOROM, but two were rated by AMSTAR 2 as moderate quality and two were found to be of critically low quality. An overall risk reduction of 34% [RR= 0.66 (0.60 - 0.73)] for all injuries and a reduction of 29% [RR= 0.71 (0.63 - 0.81)] for injuries to the lower limbs were revealed by this meta-analysis of meta-analyses. Combining every previous meta-analysis into a single source in this paper produced decisive evidence that the risk of injuries while playing soccer is reduced as a result of FIFA's injury prevention programmes

A Statistical Model to Predict the Strength Development of Geopolymer Concrete Based on SiO2/Al2O3 Ratio Variation

Geopolymer Concrete (GPC) is a new class of concrete that presents a vital improvement in sustainability and the environment, particularly in recycling and alternative construction methods. Geopolymers offer a sustainable, low energy consumption, low carbon footprint, and a 100% substitute for the Portland cement binder for civil infrastructure applications. Furthermore, many aluminosilicate materials can be obtained as by-products of other processes, such as coal combustion or the thermal pulping of wood. In addition, slag and fly ash are necessary to source materials for geopolymer. Therefore, geopolymer is considered a solution for waste management that can minimize greenhouse gas emissions. In this statistical study, the present experimental work and found experimental data were collected from local and international literature and were used to build and validate the statistical models to predict the strength development of Geopolymer concrete with binary and ternary systems of source materials. The main independent variable was R, representing the ratio of SiO2/Al2O3by weight in the source material. The investigated range of R was 1.42–3.6. Nine concrete geopolymer mixes with R in the above range represent the experimental part carried out. The targeted properties were compressive, splitting, and flexural strengths. The experimental results showed that the R ratio significantly influences the mechanical performance of the final product. The compressive strength improved by 82, 86, 93, and 95%, when metakaolin content was partially replaced by fly ash and GGBS by percentages of 30, 70, 72, 90, and 95% for mixes 2, 3, 5, 7, and 8 respectively. Also, when GGBS partially replaced fly ash content by 36% and 100% for mixes 6 and 9, compressive strength improved by 10.6% and 41.8%, respectively, compared to mix4. Furthermore, the statistical study revealed that the R ratio might be utilized to determine geopolymer strength with reasonable accuracy. The built models were developed by linear and non-linear regression analysis using SPSS software, version 25. Doi: 10.28991/CEJ-2022-08-03-04 Full Text: PD

EXPERIMENTAL INFECTION OF ARCHANOBACTERIUM PYOGENES IN ONE DAY OLD CHICKS

The present work aimed to study the pathogenicity of Archanobacterium pyogenes by using one day old chicks and chicken Embryonated eggs .The chicks were given the bacteria(4.2x108 CFU/ml) by orally administration and intrapertoneal injection, while the Embryonated eggs inoculated into allontoic sac at 12 days of incubation. The chicks were show dullness, decrease in food intake and nervous sings, most chicks were died after 2-3 days, and the bacteria were re-isolated from internal organs, and yolk sac. The inoculation of Embryonated chicken eggs resulting in embryonicdeath, reduce hatchery percentage and deformity of embryo. The study showed that A. pyogenesisvirulence to both chicken Embryonated eggs and one day old chicks

A Systematic Mapping Approach of 16q12.2/FTO and BMI in More Than 20,000 African Americans Narrows in on the Underlying Functional Variation: Results from the Population Architecture using Genomics and Epidemiology (PAGE) Study

Genetic variants in intron 1 of the fat mass- and obesity-associated (FTO) gene have been consistently associated with body mass index (BMI) in Europeans. However, follow-up studies in African Americans (AA) have shown no support for some of the most consistently BMI-associated FTO index single nucleotide polymorphisms (SNPs). This is most likely explained by different race-specific linkage disequilibrium (LD) patterns and lower correlation overall in AA, which provides the opportunity to fine-map this region and narrow in on the functional variant. To comprehensively explore the 16q12.2/FTO locus and to search for second independent signals in the broader region, we fine-mapped a 646-kb region, encompassing the large FTO gene and the flanking gene RPGRIP1L by investigating a total of 3,756 variants (1,529 genotyped and 2,227 imputed variants) in 20,488 AAs across five studies. We observed associations between BMI and variants in the known FTO intron 1 locus: the SNP with the most significant p-value, rs56137030 (8.3×10-6) had not been highlighted in previous studies. While rs56137030was correlated at r2>0.5 with 103 SNPs in Europeans (including the GWAS index SNPs), this number was reduced to 28 SNPs in AA. Among rs56137030 and the 28 correlated SNPs, six were located within candidate intronic regulatory elements, including rs1421085, for which we predicted allele-specific binding affinity for the transcription factor CUX1, which has recently been implicated in the regulation of FTO. We did not find strong evidence for a second independent signal in the broader region. In summary, this large fine-mapping study in AA has substantially reduced the number of common alleles that are likely to be functional candidates of the known FTO locus. Importantly our study demonstrated that comprehensive fine-mapping in AA provides a powerful approach to narrow in on the functional candidate(s) underlying the initial GWAS findings in European populations